We have your X8DTU-LN4F+. We used Samsung DDR3 un-buffered memory. When we use one stick it’s working fine. However, when we fully populated all memory slots, there is no POST. I checked each individual memory they all work fine. is board defective?
There is limitation on memory population. You may check the details on:
http://www.supermicro.com/support/resources/memory/X8_DP_DIMM_population.pdf
For un-buffered DIMM you would not be able to fully populate, you need to use RDIMM for such configuration.